Apparatus for reproducing from magnetic records



Jan. 26, 1965 s. I. WARMANY ETAL 3,167,752

APPARATUS FOR REPRODUCING FROM MAGNETIC RECORDS Filed July 10. 1961 FIG; I FIG. 3

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INVENTORS. STEPHEN IVAN WARMAN BY JULIUS MAGYARY ATTORNEY.

United States Patent 3,167,752 APPARATUS FOR REPRODUCING MAGNETIC RECORDS Steven Ivan Warmau and Julius Magyary, London, England, assigu'ors to Honeywell Inc., a corporation of Delaware Filed July 10, 1961, Ser. No. 122,886

' 7 Claims. (Cl. 340-4741) rnoM of the magnetic circuit, to enable thehead to produce an output dependent on the magnetism of the tape or the like even when the tape is stationary.

Several flux-sensitive read heads have been proposed. In one previously proposed head a part of the core remote from the read coil is formed with two through holes aligned in the direction of flux threading the read coil and the auxiliary winding is threaded through both holes; such a construction is illustrated in FIGURES 1 and 2 of the accompanying drawing, which show diagrammatically and in plan and elevation respectively the magnetic parts ofthe tape head. The path of the magnetic flux set up by the auxiliary winding is shown by the arrows and it will be seen that by varying the current in the auxiliary winding it is possible to saturate the shaded areas, and so vary the reluctance of the magnetic circuit threading the read coil.

The head illustrated in FIGURE 1 has been found in practice to have two main defects. Firstly the core is usually in the form of a thin strip wound fiat and thereafter bent to the approximately horse shoe shape shown.

' The edges of the holes often chafe the wires of the auxiliary windings sufficiently to rupture the insulation and set up a short circuit. Secondly it is difiicult to design the head so that current in the auxiliary winding does not saturate the area of the core between the holes before it saturates the shaded areas. Saturation of the area between the holes does not affect the magnetic circuit of .the read coil but simply prevents the flux density in r the shaded area from increasing. Thus the reluctance varying eifect of the auxiliary winding will usually be less than could be desired. a

The object of the invention is to provide a tape head which overcomes the defects of the construction discussed in the last two paragraphs.

The invention accordingly provides a flux sensitive read head (as above defined) having its auxiliary wind- "ice drawing, FIGURES 3 and 4 being respectively a diagrammatic plan and elevation of the magnetic parts of the head and FIGURE 3 being a diagrammatic elevation of the whole head.

Referring to the drawing, the core 1 comprises a strip 1 of magnetic material 40 thou (.04") wide and 1 /2 thou thick which is bent to approximately U shape. A two-part read coil is arranged with one part 2 on each arm of the U, spaced from its end: in use the tape to be read completes the magnetic circuit across the arms of the U. The strip 1 is formed at its bight with a slot 3, 1O thou wide and 30 thou long, and a mild steel rod 4, l0 thou in diameter, is welded across the slot midway in its length thus dividing the slot into two holes. An auxiliary winding 5 is wound about the rod 4.

The strip 1 is clamped in a non-magnetic body 6 by the end portions of the arms of the U, the ends themselves projecting slightly from the body. The body is generally disc-shaped with an eccentric hole 7 accommodating the bight of the U, and so placed as to define a pair of pincer elements 8 adapted to grip the strip 1 between them. At the root of one element the body is slit, as shown at 9. By driving a Wedge into the-slit the pincer element can be 'moved slightly against strip 1'to exert A threaded hole can be formed in alignment with the slit such that :a screw rethe desired gripping force.

ceived in the hole and wedging action.

As the rod 4 is round it'cannot damage the insulation of the winding 5. It is moreover easy to give it a cross section such that current in the winding saturates the areas at either side of the slot, while the rod itself is still not saturated. The material of the rod can be chosen for its welding qualities.

tightened up provides the necessary A further advantage of the construction illustrated is that on account of the rod 4 the strip 1 takes up a better shape when bent for insertion in the body 1. r

What is claimed is: I 1. 'A flux-sensitive read head responsive to the presence of an externally applied magnetic flux comprising a magnetic core arranged to define a gap therein, a read coil'wound on said core and responsive to a flux changein said core to produce an output signal, and an auxiliary flux producing means arranged to affect the overall reluctance of said core in response to a signal applied to .said auxiliary flux producing means and having an auxiliary winding threaded through two holes formed in a part of said core' remote from said read coil and aligned in the direction of flux threading said read coil, whereinv magnetic body wherein said core is mounted, the body providing a pair of pincer elements which grip between them two portions of the core adjacent the gap, said portions extending to the outside of the body.

. 4; A head as claimed, in claim 2, including a nonmagnetic bodywh erein said core is mounted, the body example in FIGURES 3, 4, and'5 of the accompanying A providing a pair of pincerjelements which grip between them two portionsof the core adjacent the gap, said I 7. A head as claimed in claim 4, whereinthe body is portions extending to the outside of the body. disc-like with an eccent'rie Circular hole receiving the 5. A head as claimed in claim 3, whereinthe body, central partof the core.

defines a slit at the baseof one pincer element and wedge I Refermes Cited fl' f this i fii means are provided to enter the slit and pivot the element 5 k V a e a to adjust the grip on'the-core portions. UNITED STATES PATENTS V t 6. A head as claimed in claim 3, w herein"the body is I 2,700,703 Nordyke Ian."25, 195$ disc-like with an eccentric circular'hole receiving the 2,704,789 Kornei Man-22, 1955 central part of the core. 1 a I 2,966,666 .Raym ond; Dad. 27, 1960 

1. A FLUX-SENSITIVE "READ" HEAD RESPONSIVE TO THE PRESENCE OF AN EXTERNALLY APPLIED MAGNETIC FLUX COMPRISING A MAGNETIC CORE ARRANGED TO DEFINE A GAP THEREIN, A READ COIL WOUND ON SAID CORE AND RESPONSIVE TO A FLUX CHANGE IN SAID CORE TO PRODUCE AN OUTPUT SIGNAL, AND AUXILIARY FLUX PRODUCING MEANS ARRANGED TO EFFECT THE OVERAL RELUCTANCE OF SAID CORE IN RESPONSE TO A SIGNAL APPLIED TO SAID AUXILIARY FLUX PRODUCING MEANS AND HAVING AN AUXILIARY WINDING THREADED THROUGH TWO HOLES FORMED IN A PART OF SAID CORE REMOTE FROM SAID "READ" COIL AND ALIGNED IN THE DIRECTION OF FLUX THREADING SAID "READ" COIL, WHEREIN SAID CORE PART HAS THE FORM OF A LONGITUDINALLY SLOTTED STRIP WITH A MAGNETIC CORE PIECE SECURED TRANSVERSELY ACROSS THE SLOT AND CARRING SAID AXILIARY WINDING. 